Common Terms.

1) XP - Experience point. Also called exp.
2) Twink - A low-level character made more powerful by higher-level characters, usually through gifts of armor and weapons that the character would not normally have at such a low level. Also used as a verb to describe the act of giving low-level characters powerful item uncommon at their level.
3) Train - To lead monsters so that they will attack another player.
4) Threat - See Hate.
5) Taunt - To provoke a monster into attacking your character, thereby pulling its attention away from its current target.
6) Tank - A character that engages in melee with  enemies and can withstand a lot of damage. Warriors and paladins are two examples of tanks. Also used as a verb to describe the act of engaging in melee  with enemies.
7) Str - An abbreviation of strength.
8) Stack - A number of identical items placed in a single inventory slot to conserve space. Only certain items can be stacked.
9) Sta - An abbreviation of stamina.
10) Spi - An abbreviation of spirit.